1. Field of the Invention
The invention relates to an ignition coil device to be used mainly in an internal combustion engine (or engine) and, more particularly, to a configuration for mounting the ignition coil device in the cylinder head of the engine.
2. Description of the Related Art
An ignition coil device of related art has a cylindrical pipe to be electrically connected with an ignition plug. Over this cylindrical pipe, there is arranged a coil tower, which includes a connector for electric connections with the outside and a flange portion to be fixed on the cylinder head. In this ignition coil device, a cylindrical pipe portion is inserted into a plug hole arranging the ignition plug while a clearance is formed therebetween, and the coil tower is arranged over the cylinder head of the engine. Moreover, a seal member is arranged below the coil tower so as to prevent water droplets from intruding into the plug hole. Since the plug hole has the waterproofing configuration therein, moreover, the seal member is provided with an air bleeding hole for preventing the deterioration of the sealing properties, as might otherwise be caused by thermal expansion or shrinkage.
JP-A-6-58237 discloses an air bleeding hole of an ignition coil device that is constituted by forming the air bleeding hole in a seal flange in parallel with the plug hole, by forming a concentric air bleeding groove in a holding plate below the coil tower, and by extending the air bleeding hole therethrough toward over the coil tower, so that the air in the plug hole may be ventilated through those groove and hole. The air bleeding hole has a complicated configuration, and the final hole opening to the atmosphere is directed upward, so that the configuration has problems in the waterproofing properties when it is employed in places of a two-wheeled vehicle or a ship, where many water droplets are splashed. In some configurations, therefore, the holes are positioned below the flange or the connector.
On the other hand, a configuration of an ignition control device disclosed in JP-A-11-191476 has two pieces of a seal member having an air bleeding hole and a rain cover, both of which bear the retention of the waterproofing properties of the plug hole. The configuration of the air bleeding hole exists in the seal member and is simple, but the rain cover needs a shape having a ring area or a straight area, which is essential in its directional determination. Moreover, the air bleeding opening and the cylinder opening are flush with each other so that the configuration easily allows introduction of water droplets in case a bank shape is absent around the cylinder hole.